Field of Invention
The present invention relates to a swash plate which is composed mainly of aluminum, suitable for use in a fixed or variable compressor, and a method of manufacturing the same.
This invention pertains to an aluminum swash plate adapted for a fixed or variable air conditioning compressor, and is particularly advantageous in terms of price competitiveness and weight reduction effects when used in lieu of conventional swash plates made of expensive copper alloy or cast iron material.
Description of Related Art
Generally, when a swash plate type compressor is used in such systems as an automobile air conditioning system, a gaseous coolant which is discharged in a low pressure state from an evaporator can be compressed into a high pressure state so as to be easily liquefied and can then be discharged into a condenser. The swash plate type compressor is provided with a piston which compresses the coolant in the compression chamber of the compressor while being moved in a reciprocal motion by the rotation of the swash plate. The swash plate which rotates in a state of being inclined relative to a driving axis is configured such that the sliding surface thereof comes into contact with the shoe of the piston and thus the piston is moved in a reciprocal fashion in the bore of a cylinder upon rotation of the swash plate. Accordingly, the lubricating properties of the sliding surface of the swash plate that comes into contact with the shoe are an important design factor in addition to mechanical properties such as wear resistance.
The material for such a swash plate includes hyper-eutectic aluminum alloy, copper alloy, and cast iron.
Specifically, the hyper-eutectic aluminum-silicon alloy used for fixed air conditioning compressors is produced by grinding silicon particles using the fast cooling rate of a continuous casting process and then performing forging. As such, in order to increase lubrication properties of the surface, a self-lubricative tin (Sn) coating process is applied (for reference, the self-lubricative coating refers to a coating process using a material that decreases friction resistance even without the application of a friction material).
However, because it is difficult for the hyper-eutectic aluminum-silicon alloy to control the size of silicon particles and is thus subjected not to typical gravity casting or sand casting but to continuous casting and forging, it is undesirably expensive compared to general aluminum products. Furthermore, seizure stress thereof is less than half of that of copper alloy or cast iron, thus making its application to variable air conditioning compressors having high surface pressure and severe driving conditions difficult.
In addition, the material of the swash plate used for variable air conditioning compressors includes copper alloy and cast iron. These two materials have superior mechanical properties and wear resistance and seizure stress, and are thus currently applied to almost all variable air conditioning compressors. However, the copper alloy is disadvantageous in terms of being more expensive than conventional cast iron or aluminum materials. In the case of cast iron, the sliding surface and the shoe in contact with each other are made of the same material and invoke seizure problems of the same kind under driving conditions, and hence, a specific coating that forms the interface between them is essential.
Taking into consideration the above, there is an urgent need to develop a swash plate made of a novel Al alloy which has higher process freedom and a lower price than the conventional hyper-eutectic aluminum-silicon alloy but has wear resistance and seizure stress equal to or superior to the copper alloy or cast iron material.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.